Barrier fabrics have been developed which impede the passage of bacteria and other contaminants and which are used for disposable medical fabrics, such as surgical drapes, disposable gowns, sterile wrap and the like. Barrier fabrics can be formed by sandwiching an inner fibrous web of thermoplastic meltblown microfibers between two outer nonwoven webs of substantially continuous thermoplastic spunbonded filaments. The fibrous meltblown web provides a barrier impervious to bacteria or other contaminants in the composite nonwoven fabric. The outer spunbonded webs are selected to provide abrasion resistance and strength to the composite fabric. Examples of such trilaminate nonwoven barrier fabrics are described in U.S. Pat. Nos. 4,041,203 and 4,863,785.
However, in addition to barrier properties and strength, medical barrier fabrics must also advantageously provide a number of other beneficial properties. For example, barrier fabrics used in medical applications must dissipate static charge because they are often used in the presence of sensitive electronic equipment and potentially volatile gases such as ether. Medical barrier fabrics must also exhibit superior fluid repellency, so that contact by water, alcohol or other organic solvents does not impair the barrier properties of the fabric.
Both static dissipation and fluid repellency have generally been imparted to medical barrier fabrics to date by applying a series of topical treatments. More specifically, antistatic performance has been imparted to medical fabrics by the application of hydrophilic coatings. Fluid repellency has been achieved in medical fabrics by the application of hydrophobic coatings. Unfortunately, the hydrophilic and hydrophobic natures of the various topical treatments are incompatible, hence the balance of properties provided to the barrier fabric is generally compromised. For example, acceptable antistatic performance may be achieved at the sacrifice of water resistance.
Fabrics rendered antistatic by means other than topical treatments are known. For example, U.S. Pat. No. 5,368,913 to Ortega discloses spunbonded fabrics for use in carpeting and the like that include conductive filaments, such as carbon or metallic filaments, distributed throughout the fabric thickness. Such fabrics can be problematic in garment applications because the electrically conductive fiber is not isolated visually or tactilely from the wearer. Conductive filaments, such as carbon or metallic filaments, are not readily dyeable and are thus generally considered to be less aesthetically pleasing than more traditional textile fibers. Carbon and metallic filaments further lack the flexibility and softness provided by traditional textile fibers. Further, fabric constructions including conductive filaments throughout their thickness generally require a significant amount of conductive filament, resulting in increased costs. The presence of conductive filaments during web manufacture can further disable the electrostatic charges frequently applied to filaments to enhance the uniformity of nonwoven webs.
Thus there remains a need in the art for improved antistatic, fluid repellent barrier fabrics.